[Comparison of effectiveness of BCG vaccination and preventive therapy in Japanese settings, with special emphasis on the sensitivity and specificity of tuberculin testing].

BACKGROUND BCG vaccination in low prevalence countries is controversial. Most discussions have been done by the comparison of benefit, side effect and cost of BCG vaccination. No discussion has been done on the disadvantage of BCG vaccination from the point of view of loss of sensitivity and specificity of tuberculin test on the diagnosis of LTBI. METHOD Three groups, i.e. the BCG vaccination group with preventive therapy under worsened sensitivity and specificity of tuberculin test due to previous BCG, no intervention group and non BCG vaccination group with preventive therapy under standard sensitivity and specificity of tuberculin test were set up. The target population was a cohort of Japanese who are born at the year with 0.1% annual risk of tuberculous infection. The TB incidence, TB related mortality (including death by BCG and preventive therapy), TB related loss of DALY (disability adjusted life years), and direct medical cost of the above three groups, for the cohort only and the cohort including secondary TB cases from the clinical cases in the cohort. RESULTS Under the current program conditions, the merit of BCG vaccination is greater than the merit obtained from the preventive therapy without BCG. Although the medical direct cost is lowest among the preventive therapy group without BCG, next without BCG or preventive therapy and highest among BCG group. Under BCG group, too extensive screening for LTBI does not reduce the loss of TB related DALY, whereas in the non BCG group, extensive screening will help to reduce the loss of TB related DALY and if more extensive screening can be done, the loss of TB related DALY in the non BCG group can be less than that in the BCG group. CONCLUSION At present extensiveness of screening for LTBI and BCG vaccination contribute to the reduction of TB and loss of TB related DALY. Possible extensive screening without BCG may be able to reduce loss of TB related DALY in comparison to the BCG vaccination group.